The Gene Targeting Core Facility (GTCF) is a fully established core resource to provide expert services for gene targeting of embryonic stem (ES) cells for the development of mouse models. The primary service provided by this core is that of taking an investigator's gene targeting vector and producing ES cell lines that can be developed into chimeric mice that transmit the pertinent genomic modification(s) through their germline. This core facility's investigators have successfully produced knockout mouse models for a variety of genes. The GTCF is an integral component of the UAB Transgenic Animal/ES Cell Resource that collectively provides expert services of not only gene targeting via the GTCF, but also blastocyst microinjection of targeted ES cell clones and DNA constructs for the production of transgenic mouse models. The Transgenic Animal/ES Cell Resource is strategically linked with other core resources at UAB including the Genetics Core of the Clinical Nutrition Research for genetic assessment, Research Animal Pathology Laboratory for phenotype assessment, and a specialized mouse-breeding core (Genetically Engineered Mouse and Marker Assisted Genetics Core). Overall, we have primer resources to make and characterize mouse models for the Center investigators.